The present invention relates to a switch for turning on and off two electric circuits by operating a common push member, particularly a time difference switch which turns on and off the respective circuits with an adequate time difference.
For example, when a driver driving an automobile in the daytime is going to inform the driver of another car ahead of him of his intention to pass, the upper head light, in other words the passing head light, is lit. For lighting the head light, two electric circuits, namely a circuit connecting the head light to the power source and a circuit for selecting the head light, are switched on and off by operating a common operating member, and in this case, a time difference switch providing an adequate time difference is used. In the conventional time difference switch for example, as shown in FIG. 7, conductive elastic movable pieces 1a and 1b, respectively associated with the two electric circuits, are united at one end and fastened to a switch base 3 at said one end 2. And, at the respective other ends, movable contacts 5a and 5b are provided to respectively move into and out of contact with the fixed contacts 4a and 4b set on the switch base 3. In addition, one of the elastic movable pieces 1a, 1b is provided with a step 6 extending toward the corresponding fixed contact 4b. The elastic movable pieces 1a and 1b are moved simultaneously toward the switch base 3 by a common push member 7, causing the respective movable contacts 5a and 5b to contact the corresponding fixed contacts 4a and 4b, for switching the circuits on. In this case, since the movable contact 5b of the elastic movable piece 1b with the step 6 contacts the fixed contact 4b before the movable contact 5a of the elastic movable piece 1a not provided with the step 6 contacts fixed contact 4a, an adequate time difference in switching on and off the two circuits is facilitated. Therefore, to ensure the adequate time difference, the step dimension must be accurately maintained.
In such a switch, said elastic movable pieces 1a and 1b are required to have a certain length, to maintain predetermined distances between the movable contacts 5a and 5b and the fixed contacts 4a and 4b during the switching off of the circuits, and to lessen the deformation of said elastic movable pieces 1a and 1b at said one end 2 caused by every switching on and off operation, for preventing the permanent deformation and fatigue failure of the elastic movable pieces 1a and 1b due to a large amount of strain. Furthermore, the sections s between the pressure points of the elastic movable pieces 1a and 1b at which the push member 7 exerts pressure and the movable contacts must also have a certain length, to establish a predetermined contact pressure and push force.
The sections s between the pressure points of the elastic movable pieces 1a and 1b at which the push member 7 exerts pressure and the movable contacts 5a and 5b are separated, and the step difference must be established over the entire sections s which are relatively long. For this reason, relative separation of said elastic movable pieces 1a and 1b due to the deformation thereof caused during production, handling, transport, etc. is liable to be large, and thus there arises a problem in that a change in step dimension and thus in time difference also becomes large. In addition, the conventional switch has another problem in that a forked push member or a push member straddling both elastic movable pieces 1a and 1b is required for simultaneously pushing both elastic movable pieces 1a and 1b.